The term deep boreholes refers in particular to petroleum, natural gas, or geothermal drilling, but also to other boreholes in which drill heads (also known as drill bits, roller bits, PDC bits, and/or any other bits of any geometry or shape) having a threaded fitting and which are capable of being screwed to another pipe element are employed. In many cases, after being screwed to the drill head, the pipe element screwed to the drill head is screwed at its opposite end to a further pipe element which is usually of identical design. This operation is then repeated multiple times in order to form a long drill string composed of a multiplicity of pipe elements, having a drill head at the lower end. The elements described above as “pipe elements” henceforth will be referred to as “elements of the drill string”. These elements need not necessarily be “pipes” in the conventional sense. Instead of “pipes” any other elongate elements which are suited to a drill string may also be used. These substantially include rotationally symmetrical bodies which are interconnectable in the longitudinal direction. Pipe lengths may be between 9 meters and 13.5 meters.
The method which is carried out using a drill string as described above is also referred to as a “rotary method”. A drill string henceforth is also referred to as a “drill pipe”.
A few construction details pertaining to the described (pipe) elements of the drill string and to the assembly and disassembly of these elements of the drill string are described in patent application DE 10 2011 052 695. Reference is hereby made to the contents of this patent application. They form a composite part of this disclosure.
For many years, the interconnection of the elements of the drill string has been performed with the aid of clamping-screwing devices in so-called drill rigs. The term clamping-screwing devices in particular refers to the devices which in the technical terminology are referred to as “iron roughnecks” or as “hydraulic roughnecks”. A known “iron roughneck” in the context of the system described herein usually comprises a high-speed rotating device (most often configured as a friction gear) which is referred to as a “spinner” and which usually engages in the lower region of the elements of the drill string and rapidly drives the latter which is suspended in a drill rig, in order to perform a first part of a screwing operation. This “iron roughneck” furthermore comprises a first clamping device for holding a first end of an element of a drill string in a clamping manner, as well as a second clamping device for holding a second end of an element of a drill string in a clamping manner. The first clamping device and the second clamping device, which are also referred to as “tongs” are mounted so as to be rotatable or pivotable, respectively, and are in particular employed for the second part of a screwing operation, in order to tighten the elements of the drill string which have already been screwed together with the aid of the “spinner”, using a specific, predetermined torque. Therefore, using the “tongs”, particular accuracy and thus high reliability of the screw joints are achieved.
The screw joint of the drill head with the lowermost element of a drill string to date mostly takes place with the aid of very large tongs which are usually referred to as “manual tongs” and are operated using muscle power or with the aid of hydraulic or, optionally, electric drives. In a complementary manner to the “manual tongs”, so-called “bit crushing plates” are also employed. It is disadvantageous in the methods employed to date for connecting a drill head to an element of a drill string that said methods are very personnel and time intensive.
Further details pertaining to the clamping-screwing devices known from the prior art are disclosed in U.S. Pat. No. 7,062,991 B1 and from US 2002/0062717 A1.
U.S. Pat. No. 7,062,991 B1 particularly refers to the use of a plate which is mounted in lateral guide rails of a clamping-screwing device and which is employed in the context of the crushing plates mentioned above.
US 2002/0062717 A1 likewise refers to crushing plates, wherein the crushing plates are provided with anti-twist rods referred to as “torque transfer arms” which, together with receiving openings which are configured on the clamping-screwing device described in the document, are usable as momentum support for the crushing plates once the latter have been moved into one another.
Accordingly, it is desirable to provide a method as well as a device for holding a drill head provided for ground boreholes in a force-fitting or form-fitting manner, which both simplify connecting a drill head to an element of a drill pipe.